1. Technical Field
This invention relates to a seal system design for use in the completion and production operations of oil and gas wells wherein the seal is comprised of a plurality of plastically deformable members comprised of alternating seal rings of different materials utilized to sealing engage moveable wellbore members.
2. Description of the Related Art
Prior art sealing assemblies have been used to sealingly engaged moveable members in wellbore tools. These prior art sealing assemblies fail to perform after prolonged exposure to wellbore temperatures and pressures, some failing after minimal exposure to wellbore conditions. None of these prior art sealing assemblies reliably sealingly engaged noncontinuously mating moveable members after several mating engagements.
One example of a prior art sealing assembly would be the Conduit Sealing System of the Amancharla Patent, U.S. Pat. No. 4,234,197, disclosing a sealing assembly comprised of several types of materials. One of these materials is a perfluoroelastomer sold by DuPont under the trademark KALREZ. Although this material has high thermal stability and excellent chemical resistance, it is an elastomeric material which after prolonged exposure to wellbore temperatures will harden, become brittle, and fail to provide a dynamic sealing engagement with moveable wellbore surfaces.
Another example of a prior art sealing device is the Plastically Deformable Conduit Seal For Subterranean Wells disclosed in the Allison Patent issued as U.S. Pat. No. 4,406,469. This patent disclosed a self-energizing sealing system employing plastically deformable nonelastomeric elements to establish sealing integrity between concentric, relatively moveable tubular conduits. This prior art self-energizing sealing system, or sealing apparatus, is comprised of a plurality of sealing members including chevron-shaped thermoplastic members, and high temperature thermoplastic members made of polyphenylene sulfide resin sold under the trademark RYTON. Although RYTON members provide support to prevent extrusion of regular service temperature sealing members, they do not sealingly engage repeatably slidable moving surfaces to prevent wellbore pressures from damaging regular service temperature sealing members. In fact, testing in the development of the current invention indicated that this sealing apparatus failed to reliably perform after several actuations of a moveable member when mating between sealing elements and surfaces to be sealed was not continuous.
In addition, various prior art sealing assemblies were tested. None of these prior art sealing assemblies would perform reliably after temperature thermocycling, prolonged exposure to high temperature, and repeated actuation of noncontinuously mated moveable members for more than five cycles of actuation. Most of the prior art sealing assemblies failed to perform after one or two actuations.